肠道微生物对草鱼呼肠孤病毒(GCRV)感染的响应机制研究

Grass carp (Ctenopharyngodon idellus) is on the top of freshwater fish yield in the world. The grass carp hemorrhagic disease caused by grass carp reovirus (GCRV) is the most serious problem in grass carp aquaculture, but unfortunately, there is still lacking of useful method to solve this disease problem. As gut microbiota can regulate host’s immune response to enhance animal’s resistance to diseases, this proposal tends to study the responses of gut microbiota to GCRV infection. This study will give some valuable references for effective prevention of grass carp hemorrhagic disease from the new aspect of gut microbiota. Specifically, this study will focus on the response mechanism of gut microbiota in grass carp that manually infected with GCRV. Generally, only a few of individuals that infected by GCRV can recover successfully, but most of infected grass carp will die quickly within two weeks. We will monitor the succession of gut microbiota in grass carp across the recovery. The gut microbiota composition, key species/strains, core functional gene expression, as well as important metabolites will be investigated by using the amplicon sequencing, metagenomic sequencing, metatranscriptomic sequencing, and metabolite analysis, respectively. Combining the detected variation of grass carp immune factors and important immune gene expression at corresponding stages, the response mechanisms of gut microbiota to GCRV infection will be elucidated. This study will not only correlate the gut microbiota with host immunity, but also further reveal how gut microbes help host recovery from GCRV infection. This study will strengthen our understanding of mechanism how fish gut microbes help the host to resist infection of virus, it also can provide references for effective prevention of grass carp hemorrhage in aquaculture.

草鱼是世界上产量最大的淡水养殖鱼类，其养殖过程面临的最主要病害是由GCRV引起的草鱼出血病，目前尚没有能彻底解决这一问题的有效措施。由于肠道微生物能调节宿主免疫反应并提高对疾病的抵抗能力，本项目拟通过揭示肠道微生物对草鱼感染GCRV的响应机制，为草鱼出血病的有效预防提供新对策。具体以人工感染GCRV草鱼为对象，利用扩增子、宏基因组、宏转录组测序及代谢产物分析等，揭示感染病毒草鱼在恢复健康过程不同状态下肠道微生物组成、关键菌种、核心基因表达及代谢产物变化规律；结合对应阶段草鱼免疫相关指标及关键免疫因子表达结果，通过与对照组草鱼的系统比较阐明肠道微生物在草鱼感染病毒后的响应机制及其对草鱼免疫力的影响。本研究创新之处在于明晰感染病毒草鱼肠道微生物如何响应并发挥功能协助草鱼恢复健康，这不仅能加强对鱼类肠道微生物助力宿主抗病毒机制的认识，而且可为有效防治草鱼出血病这一重要养殖病害提供科学依据。

草鱼是世界上产量最大的淡水养殖鱼类，其养殖过程面临的最主要病害是由GCRV引起的草鱼出血病，目前尚没有能彻底解决这一问题的有效措施。由于肠道微生物能调节宿主免疫反应并提高对疾病的抵抗能力，本项目通过研究人工感染GCRV-Ⅱ对草鱼免疫的影响及肠道菌群的响应机制研究发现，GCRV-Ⅱ感染后表现出严重出血症状的草鱼具有明显不同的肠道微生物菌群且α多样性最低，肠道中革兰氏阴性厌氧菌——鲸杆菌属(Cetobacterium)丰度显著增加，肠道微生物的均质扩散程度最高。结合对草鱼肠道和脾脏组织的转录组测序分析发现，草鱼的NOD样受体(NLRs)、Toll样受体(TLRs)和脂多糖(LPS)相关通路基因在GCRV-Ⅱ感染后出现严重出血症状的草鱼中显著上调，且与肠道核心微生物鲸杆菌属和不动杆菌属(Acinetobacter)显著正相关。进一步分析表明GCRV-Ⅱ感染草鱼后导致的厌氧菌C. somerae剧增又会导致LPS异常增加，进而通过LPS相关的NLRs和TLRs途径加重宿主炎症反应。本研究阐明了肠道微生物对草鱼感染GCRV-Ⅱ的响应机制，这不仅能加强对鱼类肠道微生物助力宿主抗病毒机制的认识，而且可为草鱼出血病这一重要养殖病害的生态防控提供科学依据。本项目相关研究结果已发表标注本项目(31802350)资助的SCI论文13篇(其中第一标注5篇，第二标注7篇，第三标注1篇)；已培养出站博士后1名、已毕业博士生1名、已毕业硕士生3名，超额完成了项目目标任务。

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